Description of the Prior Art
It is well known that the useful life of large diameter pipes, such as sewage pipes, water conduits, and the like, can be prolonged by coating their interiors with a protective lining, thereby preventing corrosion. Consequently, numerous apparatus and devices have been proposed to perform this coating operation. Typically a vehicle of some kind is provided with an application head, or distributor, which applies fluent coating material radially outward, and the vehicle is made to pass through the interior of the pipe. Troweling arrangements are frequently provided as well to smooth the surface of the applied coating, after which the coating is allowed to harden. Such a device is disclosed in U.S. Pat. No. 3,810,441 which issued on May 14, 1974 to Clifford A. Padgett.
Such pipes can be quite large, however, diameters of five feet and more not being uncommon, and the lining devices for such pipes must therefore also be quite large. This gives rise to problems in transferring either the lengths of pipe and/or the lining vehicle between lining operations and also in aligning the two once they are brought together. A proposed approach to this problem is disclosed in U.S. Pat. No. 3,164,491 which issued on Jan. 5, 1965 to Jay K. Brockett et al. According to this patent, a length of straight track is laid extending toward an apparatus for supporting a length of pipe and rotating it about its central axis. A special cleaning and lining vehicle is provided having a "primary carriage" which rides on the track. A long boom which extends from the primary carriage carries a cleaning/lining apparatus which is inserted into the length of pipe as the primary carriage is advanced along the track. The cleaning and lining operation is performed as the apparatus is backed out of the pipe and the pipe is rotated.
While this arrangement appears to facilitate aligning the lining apparatus and the pipe, it presents a disadvantage in that it necessitates considerable handling of the pipe, including lifting and transporting, both before and after the lining operation. Not only is this time consuming, but it also creates a risk of dislodging the applied coating before it was hardened, which would necessitate costly and time consuming recleaning and relining of the pipe.
Another problem presented in the use of these lining arrangements is that of delivering sufficient lining material to the lining machine so that the lining operation can be performed in one pass through the pipe. U.S. Pat. No. 2,261,928 which issued on Nov. 4, 1941 to A. G. Perkins et al. discloses a pipe lining vehicle which has a centrifugal type applicator and trailing troweling arrangement. The vehicle supports two interconnected cement mixing "hoppers", the more forward of the two being placed somewhat higher on the vehicle than the more rearward one. A pair of "feed pipes" convey cement and water to the forward hopper where it is mixed by rotating paddles. When this hopper is sufficiently full the cement mixture is picked up by a screw conveyor which passes the mixture to the rearward hopper, where it presumably falls to the bottom thereof by gravitational action. It is there further mixed by a second rotating paddle arrangement. Finally, the mixture is picked up by a second screw conveyor, apparently larger than the first, which feeds the mixture through a conduit to the applicator. The vehicle travels in the pipe on two sets of support wheels plus a fifth, centrally located steering wheel. This device requires cement to be fed to it from an external source as it performs the lining operation, which necessitates the handling of flexible tubes and the like. In addition, the device is apparently unstable on level ground because of the central steering wheel which extends below the support wheels in order to contact the pipe.
There is thus a need for an improvement to pipe lining apparatus which permits a pipe lining apparatus to be conveyed easily and conveniently to lengths of pipe.
There is further need for an improvement to pipe lining apparatus which permits facilitated alignment of a pipe lining apparatus and a length of pipe.
There is a still further need to provide an improvement to pipe lining apparatus which eliminates the need for handling tubes and conduits for fluid lining material during a lining operation while permitting a complete lining operation in one pass of a lining apparatus through a length of pipe.